It is known that current automotive systems are equipped with exhaust gas aftertreatment systems. Among the various aftertreatment devices, Lean NOx Traps (LNT) may be used. A Lean NOx Trap (LNT) is a catalytic device containing catalysts, such as Rhodium, Pt and Pd, and adsorbents, such as barium based elements, which provide active sites suitable for binding the nitrogen oxides (NOx) contained in the exhaust gas, in order to trap them within the device itself. However, when NOx storage in the LNT approaches its limit, LNT efficiency drops.
A LNT can be regenerated by the activation of a rich combustion mode, called DeNOx regeneration. During a DeNOx regeneration, emission levels increase significantly, especially Hydrocarbon (HC), Carbon Oxide (CO) and smoke. Since a rich combustion mode is created by injecting fuel in to the exhaust gas stream, either by after injections, namely by fuel injections in the cylinders of the engine that occur after the Top Dead Center (TDC) of the respective piston or by a dedicated injector, fuel consumption is also increased during rich phases.
Current DeNOx regeneration strategies initiate a DeNOx regeneration event when the LNT is supposed to be full of NOx and if predefined conditions about temperature and combustion stability are satisfied. However, in real driving conditions there is a high probability of undesired DeNOx regenerations interruptions, for example during urban driving or in other unfavorable conditions. When a DeNOx event is interrupted, emission levels and fuel consumption may still be higher than desired, with limited benefits in terms of NOx reduction
Accordingly, there is a need in the art to provide a strategy that allows a substantial improvement in the management of DeNOx regeneration events according to the actual driving conditions of the vehicle. There is also a need in the art to define a strategy for the management of DeNOx regeneration events that does not impact significantly on fuel consumption.